/
attributes.rs
157 lines (140 loc) · 4.87 KB
/
attributes.rs
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use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::{
parse::{Parse, ParseStream},
punctuated::Punctuated,
spanned::Spanned,
token::Comma,
Attribute, Expr, ExprPath, Ident, LitStr, Path, Result, Token,
};
pub mod kw {
syn::custom_keyword!(annotation);
syn::custom_keyword!(attribute);
syn::custom_keyword!(dict);
syn::custom_keyword!(extends);
syn::custom_keyword!(freelist);
syn::custom_keyword!(from_py_with);
syn::custom_keyword!(gc);
syn::custom_keyword!(get);
syn::custom_keyword!(item);
syn::custom_keyword!(mapping);
syn::custom_keyword!(module);
syn::custom_keyword!(name);
syn::custom_keyword!(pass_module);
syn::custom_keyword!(set);
syn::custom_keyword!(signature);
syn::custom_keyword!(subclass);
syn::custom_keyword!(text_signature);
syn::custom_keyword!(transparent);
syn::custom_keyword!(unsendable);
syn::custom_keyword!(weakref);
syn::custom_keyword!(immutable);
}
#[derive(Clone, Debug)]
pub struct KeywordAttribute<K, V> {
pub kw: K,
pub value: V,
}
/// A helper type which parses the inner type via a literal string
/// e.g. LitStrValue<Path> -> parses "some::path" in quotes.
#[derive(Clone, Debug, PartialEq)]
pub struct LitStrValue<T>(pub T);
impl<T: Parse> Parse for LitStrValue<T> {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let lit_str: LitStr = input.parse()?;
lit_str.parse().map(LitStrValue)
}
}
impl<T: ToTokens> ToTokens for LitStrValue<T> {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.0.to_tokens(tokens)
}
}
/// A helper type which parses a name via a literal string
#[derive(Clone, Debug, PartialEq)]
pub struct NameLitStr(pub Ident);
impl Parse for NameLitStr {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let string_literal: LitStr = input.parse()?;
if let Ok(ident) = string_literal.parse() {
Ok(NameLitStr(ident))
} else {
bail_spanned!(string_literal.span() => "expected a single identifier in double quotes")
}
}
}
impl ToTokens for NameLitStr {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.0.to_tokens(tokens)
}
}
pub type ExtendsAttribute = KeywordAttribute<kw::extends, Path>;
pub type FreelistAttribute = KeywordAttribute<kw::freelist, Box<Expr>>;
pub type ModuleAttribute = KeywordAttribute<kw::module, LitStr>;
pub type NameAttribute = KeywordAttribute<kw::name, NameLitStr>;
pub type TextSignatureAttribute = KeywordAttribute<kw::text_signature, LitStr>;
impl<K: Parse + std::fmt::Debug, V: Parse> Parse for KeywordAttribute<K, V> {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let kw: K = input.parse()?;
let _: Token![=] = input.parse()?;
let value = input.parse()?;
Ok(KeywordAttribute { kw, value })
}
}
impl<K: ToTokens, V: ToTokens> ToTokens for KeywordAttribute<K, V> {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.kw.to_tokens(tokens);
Token![=](self.kw.span()).to_tokens(tokens);
self.value.to_tokens(tokens);
}
}
pub type FromPyWithAttribute = KeywordAttribute<kw::from_py_with, LitStrValue<ExprPath>>;
/// For specifying the path to the pyo3 crate.
pub type CrateAttribute = KeywordAttribute<Token![crate], LitStrValue<Path>>;
pub fn get_pyo3_options<T: Parse>(attr: &syn::Attribute) -> Result<Option<Punctuated<T, Comma>>> {
if is_attribute_ident(attr, "pyo3") {
attr.parse_args_with(Punctuated::parse_terminated).map(Some)
} else {
Ok(None)
}
}
pub fn is_attribute_ident(attr: &syn::Attribute, name: &str) -> bool {
if let Some(path_segment) = attr.path.segments.last() {
attr.path.segments.len() == 1 && path_segment.ident == name
} else {
false
}
}
/// Takes attributes from an attribute vector.
///
/// For each attribute in `attrs`, `extractor` is called. If `extractor` returns `Ok(true)`, then
/// the attribute will be removed from the vector.
///
/// This is similar to `Vec::retain` except the closure is fallible and the condition is reversed.
/// (In `retain`, returning `true` keeps the element, here it removes it.)
pub fn take_attributes(
attrs: &mut Vec<Attribute>,
mut extractor: impl FnMut(&Attribute) -> Result<bool>,
) -> Result<()> {
*attrs = attrs
.drain(..)
.filter_map(|attr| {
extractor(&attr)
.map(move |attribute_handled| if attribute_handled { None } else { Some(attr) })
.transpose()
})
.collect::<Result<_>>()?;
Ok(())
}
pub fn take_pyo3_options<T: Parse>(attrs: &mut Vec<syn::Attribute>) -> Result<Vec<T>> {
let mut out = Vec::new();
take_attributes(attrs, |attr| {
if let Some(options) = get_pyo3_options(attr)? {
out.extend(options.into_iter());
Ok(true)
} else {
Ok(false)
}
})?;
Ok(out)
}